MOSFET polarity AND over voltage protection?

[FiveseveN]

Trying to implement both functions with a single pass-through element, I've been playing with this circuit in simulation for now, don't have the parts to breadboard it at the moment. uCap shows it working, if somewhat iffy. Tried it in Falstad but the OVP doesn't work at all there  . Zeners are 5.6V each. Any thoughts?

[Rob Strand]

R3 needs to be smaller so a reasonable current is passed through the zener(s), say 1k.
Source to input supply.

See,




Don't do it like this.  Too much current will flow through the zener.
This one has the MOSFET detail correct.

[antonis]

Shouldn't a crowbar need less items..??

[Rob Strand]

Shouldn't a crowbar need less items..??

It's not a crowbar.  It opens the MOSFET when there is overvoltage, much kinder than crowbar.